At the top of the conversation screen Viber will notify you that the sender is not in your contact list. The conversation screen will also display three options at the top: Add to contacts, Report spam, and Block.
If the message is spam you can choose to report spam. This will report the spammer to our servers at Viber as well as block the user from further messaging you.
If you just wish to block the user, click the block button and the number will be blocked from further contacting you.
You can block users that are participating in the same group as you through the group information screen.
Enter the group > Swipe the screen left > Click on the contact > SelectView Info > Click the more button > Select “Block” (Depending on your device, the menu button may appear at the top right of the screen or at the bottom left of the device, as shown below).
The blocked contact will still be able to see your activity within the group and you will be able to see theirs.
The block will only apply to one-on-one conversation attempts
Open the conversation screen
Swipe the screen left
Go to the More screen
Open the Settings menu
Click on the plus (+) sign on the top right and select the contact or add the phone number you wish to block. Remember to enter the number in the following format: + Country Code – Area Code – Phone Number. For example, the US number 1-234-567-8910 should be entered as +12345678910.
How do I unblock a contact?
Select More Options menu
Select Block List
Find the contact you wish to unblock
Will the blocked contact know that I have blocked them?